1. Field of the Invention
The present invention relates to a reinforcing material for a kneaded and formed hydraulic material, and a kneaded and formed article.
2. Description of the Background
Fiber has been used as a reinforcing material for a hydraulic material, such as cement and gypsum, for a some time.
For example, JP 54-31421 discloses a fiber-reinforced paper-manufactured cement plate mixed with polyvinyl alcohol based fiber having a fineness of from 15-25 d, a strength of 9 g/d or more, and an elongation of from 5-10%. In the case where a paper-manufacturing method is employed, in which a slurry comprising fiber and a hydraulic material dispersed in water is paper-manufactured, the fiber is two-dimensionally oriented in the direction of extension of the article which is formed, to effectively exhibit the reinforcing effect. However, in the case where a kneading and forming method is employed, in which the fiber is uniformly blended in a matrix, since the fiber is three-dimensionally and randomly dispersed in the cement, it is difficult for the fiber to exert a sufficient and practical reinforcing effect in the attempt to prepare a kneaded and formed article having a high toughness.
JP 56-125269 discloses a paper-manufactured cement plate and a kneaded and formed article therefrom using PVA based fiber having a fineness of from 1-4 d, a strength of from 8-9 g/d, and an elongation of from 5-6%. Although a formed paper-manufactured article prepared by this method exhibits excellent performance characteristics, when the procedure of kneading and forming is conducted, problems such as the formation of fiber balls occurs because of the small diameter of the fibers. The result is that a sufficient reinforcing effect cannot be obtained.
JP 59-8664 discloses a hardened hydraulic article obtained by kneading and forming a PVA based fiber having a fineness of from 100-1,000 d and an aspect ratio of from 30-150 in a matrix material. Further, JP 63-303837 describes a hardened hydraulic article obtained by kneading and forming a matrix material containing PVA based fibers having a fineness of from 1,000-9,000 d and an aspect ratio of from 20-150. The fiber of the product has a high tenacity and a high modulus of elasticity. However, when a fiber having only a high tenacity and a high modulus of elasticity is used to prepare an article, or the adhesion of the fiber to the matrix is increased, the toughness of the kneaded and formed article cannot be sufficiently be improved, because when a bending stress is applied to the kneaded and formed article, the PVA fiber has a tendency to break before it is able to exhibit its inherent strength.